1. Field of the Invention
The present invention relates to a process for making selected polyalkoxylated glucosides. Furthermore, the present invention also relates to polyalkoxylated glucosides as prepared by this process and their use as surfactants in enhanced oil recovery processes.
2. Brief Description of the Prior Art
Surfactants are commonly used agents employed in a wide variety of commercial processes and products. In the field of enhanced oil recovery, both anionic and nonionic surfactants are being employed. See U.S. Pat. No. 4,371,444, which issued to McCoy and Naylor on Feb. 1, 1983 and is incorporated herein by reference in its entirety.
Surfactants used in enhanced oil recovery applications are required to have certain properties. First, they should reduce the interfacial tension values between the crude oil and the aqueous drive fluid used for recovery, thereby causing good emulsification of the crude oil in the drive fluid. Second, they should stay soluble at the high temperatures sometimes experienced in the oil-bearing rock formations. Third, they should remain stable and effective even in the presence of high ionic strength materials (e.g. monovalent ions such as Na.sup.+, Cl.sup.- and OH.sup.- and divalent ions such as Ca.sup.++ and Mg.sup.++) which may also be present during operations. Fourth, the cost of these surfactants should be low enough to justify recovery of the additional oil.
While there are surfactants that meet these requirements under certain operating conditions, there is a strong need for surfactants which are effective over wider or different ranges of operating conditions, particularly at high salinities and high temperatures.
Glucoside-based surfactants have a high tolerance to strong ionic strength solutions as well as having good solubility in aqueous solutions. These characteristics are due at least in part to their multi-hydroxyl functionality.
U.S. Pat. No. 3,640,998, which issued to Mansfield and Rainey on Feb. 8, 1972, teaches the preparation of surface active compositions comprising mixtures of alkylene oxide adducts of alkyl oligosaccharides, alkyl glucosides and alkanols. These surface active compositions are made by (1) preparing a mixture of lower alkyl oligosaccharides and a lower alkyl glucoside by a conventional Fischer-type reaction of one mole of glucose with 1 to 12 moles of a lower alkanol; (2) then replacing the lower alkyl groups with higher primary alcohol groups (C.sub.8 to C.sub.32) by means of an alcohol interchange reaction (transacetalation); followed by (c) introducing lower alkylene oxide groups onto the components of the group.
This disclosed synthesis has several significant limitations. First, a mixture of several compounds is made instead of one product or primarily one product. In fact, the patent teaches the relative amounts of the formed alcohol, alkyl glucoside and alkyl oligosaccharide components are determined by the mole ratio of alcohol/glucose and the extent of the transacetalation reaction (See column 3, lines 13-20 and lines 51-58 of the patent). Also, the attachment of the long hydrocarbon chain moiety requires two addition stages and the interchange of alcohols. These steps may lead to the decomposition of the glucoside moiety or the formation of unwanted by-products or both. Still further, the synthesis is limited to placing only saturated aliphatic hydrocarbon radicals ranging from C.sub.8 H.sub.17 to C.sub.32 H.sub.65 by the alcohol interchange reaction. The synthesis does not provide for the introduction of unsaturated or aryl groups as part of alcohol.